This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2001-320999, filed Oct. 18, 2001, the entire contents of the application are incorporated herein by reference.
1. Field of the Invention
The present invention relates to a photometric apparatus for photographic equipment, particularly to a photometric apparatus having a backlight evaluation function.
2. Description of Related Art
The faces of people as the main subject of a picture are not well reproduced when a picture is taken in backlight using the same exposure condition as in the normal light. Therefore, a strobe emission and exposure control are required with the backlight. One of the solutions is disclosed in the U.S. Pat. No. 5,258,803. This patent discloses a camera in which the photographic frame is divided into a plurality of photometric areas and the focal point is also detected for several photometric areas that are around the center of the photographic frame. The camera uses photometric measurements for the areas that are actually used for detecting the focal point (that are selected among the photometric areas available for the focal point detection depending on the operational mode), the average photometric measurement among a certain number of surrounding areas of the above mentioned areas, the average photometric measurement among the other areas, and the maximum photometric measurement in all the areas to evaluate the backlight condition and control the strobe and exposure.
However, the method disclosed in the ""803 patent above expects the subject to always be in the middle of the photographic frame. It does not take into account the size of the subject in the photographic frame. Therefore, the backlight may be mistakenly confirmed when the subject is in the margin of the photographic frame or occupies a large part of it, leading to erroneous control of the strobe and exposure.
In view of the above problems, the present invention aims to provide a photometric apparatus for a camera that enables highly precise exposure control under backlight conditions.
The present invention uses a photometric part for measuring the brightness in a plurality of areas of the photographic range as well as a geometric part for measuring the distance to the subject in a plurality of areas of the photographic range in a photometric apparatus, such as a camera. The geometric results from the geometric part are used to select an area corresponding to the main subject in the photographic range and the brightness of the selected area are used for exposure control. In representative embodiments, the present invention compares the brightness of the selected area with that of the other areas for evaluating the backlight.
The present invention selects an area corresponding to the main subject in the photographic range. Therefore, the main subject is not necessarily at the center of the photographic range.
Preferably, the position of the main object in the photographic range is detected, to use as an evaluation factor. With this configuration, for example, considering that a main subject is highly likely near the center of the frame, a subject near the center of the frame tends to be considered to be the main subject, more than one located in the margin in order to improve the recognition of the main subject.
Preferably, the size of the main object in the photographic range is detected to use it as an evaluation factor. With this configuration, for example, considering that it is highly unlikely that a main subject occupies the entire frame, the recognition of the backlight condition is set to be easy for a larger subject rather than a smaller one in order to improve the recognition of the main subject.
Conditions regarding the position and size of a main subject in the photographic range may be conveniently stored in a table form.
The focal length and F number of the photographic lens and distances to the main subject are preferably taken into account to evaluate the backlight in order to improve the recognition of the main subject.
A main subject is preferably found in the photographic range by selecting the subject in the areas of geometric data which are within a certain range. First, an area having the closest subject is detected and, then, in the adjacent areas, the distances to the subject which are within a certain range from the smallest distance are selected.
In addition to distance data, color, brightness, and pattern of the parts in interest can be used to improve the recognition of the main subject although this complicates the apparatus.
The present invention is not confined to selecting areas including the main subject. A larger area, for example an area that is not preferred to be seen black because of backlight, can be selected.
The photometric apparatus of the present invention has application in devices such as film cameras, digital cameras, video cameras, and photographic units installed in (or mounted on) PDAs, cellular phones, and personal computers.